Occurrence of Glyphosate in Groundwater and Surface Water Within Farming Communities in Central Tongu District, Ghana
Date
2016-10
Authors
Journal Title
Journal ISSN
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Publisher
University of Ghana
Abstract
The study investigated the occurrence/presence of glyphosate residues in groundwater and surface
water from selected farming (Pepper, Maize and Cassava) communities within the Central Tongu district of Ghana. The study also evaluated the potential health risk posed to children and adults
through drinking of ground and surface water. This was achieved through: (i) assessment of the
levels of glyphosate residues in groundwater (Boreholes) and surface water within farming
communities of Central Tongu; (ii) appraisal of physical parameters of the waters, as well as
assessment of their influence on the levels of glyphosate residues via Principal Component
Analysis (PCA); (iii) investigation of the relationship between glyphosate levels and water
resources within Central Tongu district using Hierarchical Cluster Analysis (HCA); and, (iv)
estimation of the Human Health Risk associated with consumption of groundwater (Borehole)
and surface water by inhabitants (children and adults). Glyphosate residue levels were determined
by LC-MS/MS; after extraction of glyphosate residues from water using dichloromethane. pH,
Temperature, Salinity, Conductivity and Total Dissolved Solids (TDS) were measured on-site
using LaMotte PockeTester Multi-meter. The pH of the borehole samples ranged from slightly
acidic (5.69) to near neutral (7.4); whiles the pH of the surface water samples ranged from near
neutral (7.35) to weakly basic (8.0). Temperature of borehole samples was between 29.7 to 33.5
℃. The temperature of the surface water samples was also between 30.5 ℃ and 31.8 ℃.
Conductivity of surface water ranged from 1025 to 1175 μS/cm; with that for groundwater samples
(Borehole) ranging from 1350 - 11320 μS/cm. Salinity ranged from 450 to 570 mg/L; and 640 and
6640 mg/L for surface water and groundwater (Borehole) respectively. TDS for surface water
ranged from 670 to 850 mg/L; and 920 to 7780 mg/L for borehole samples. Levels of glyphosate
residues (Groundwater: 2.57 - 9.21 μg/L; Surface water: 25.10 - 42.50 μg/L) obtained were below
the 280 μg/L Recommended Guideline Value for Canada; and the USEPA Maximum Allowed Concentration of 700 μg/L. However, the levels of glyphosate residue obtained were higher than
the recommended 0.1 μg/L glyphosate residue in drinking water by the European Union. pH was
identified as the sole physicochemical parameter influencing glyphosate residues in the water
resources (through Principal Component Analysis [PCA]). Glyphosate residues were high in
slightly basic water samples; and low in slightly acidic water samples. Hierarchical Cluster
Analysis (HCA) also established close association between levels of glyphosate and the type of
Water resources. The levels of glyphosate in groundwater were relatively low compared to the
high levels of glyphosate in surface water. Assessment of Non-carcinogenic Risk using Hazard
Quotient (HQ) for acute and chronic exposures revealed some level of risk associated with the
consumption of groundwater and surface water from the selected farming communities in the
Central Tongu district. For acute exposure, the HQ for groundwater ranged from 0.18 to 0.65 for
adults; 0.36 - 0.80 and 1.19 - 1.29 (for two communities; Bakpa Dzave and Kanikope) for children.
For surface water, HQ ranged from 1.77 - 3.01 (Adults) and 3.51 - 5.95 (Children). For chronic
exposure, the HQ for groundwater ranged from 0.05 - 0.19 (Adults) and 0.10 - 0.37 (Children);
whiles the HQ for surface water ranged from 0.51 - 0.86 and 1.00 - 1.70 for adults and children
respectively. Groundwater/borehole water did not pose any potential health risk to both adults and
children from chronic exposure. Though surface water did not pose any potential health risk
chronically to adults; children are at risk. For acute exposure, borehole water did not pose a
potential health risk to both adults and children; notwithstanding, children in Bakpa-Dzave and
Kanikope were at risk. Acute exposure to surface water poses a potential health risk to both adults
and children.
Description
MPhil. Nuclear and Environmental Protection
Keywords
Ghana, Central Tongu District, Groundwater, Surface water, Glyphosate residues